If you are interested in checking out AutoCAD Plant 3D and giving us feedback please check it out. In it you can see how to create specs, place equipment, model basic structures, route pipe, and all sorts of other groovy piping stuff (though not isometrics - it's coming - promise!). You can download the Alpha 1 from https://myfeedback.autodesk.com under the Stella Project. There is also a preview guide posted to help you get started.
To get on the Stella Project, you need to sign up for Stella Alphas and Betas. You do this by modifying your MyFeedback profile (press the User button) to include the words Stella Alpha in the Beta Code field of your profile. About a day later you should see the Stella Project as one of the options under your MyFeedback Zones.
Alternatively, if you happen to be attending Autodesk University in Las Vegas during the first week of December (only 69 days away!), you will be able to check out Stella there also. We're planning test drives and focus groups and all sorts of other groovy stuff for AU 2008.